(1) Field of the Invention
The invention is in the field of drywall interior ceilings.
Preformed panels of drywall, sometimes called plasterboard, are affixed by self-tapping screws to a metallic grid suspended below a structural ceiling. The screws pass through flanges of beams in the grid.
In short spans of ceiling, the beams are suspended only on a molding extending along the walls. On long spans of ceiling, the beams are also suspended between the walls by wires embedded in the structural ceiling.
(2) The Prior Art
There is shown in U.S. Pat. No. 6,722,098, incorporated herein by reference, a beam for a grid in a ceiling that has panels of drywall affixed to the ceiling grid by self-tapping screws. Such beams generally extend from wall to wall in a room, and rest on a wall molding having a right angle in its cross section, with the vertical leg of the angle affixed to the wall, and a horizontal ledge extending from the wall.
The end of a beam rests on the ledge and is affixed to the ledge by, for instance, a self-tapping screw.
It is important that the beams be accurately spaced, and parallel to one another at, for instance, a 4′ distance, since the panels are generally 4′×8′ in dimension, and it is necessary for the edge of a panel to be positioned directly below a beam for attachment thereto.
Additional beams are also generally located at regular intervals, between, and parallel to, the four foot spaced beams, to provide more beams to which the panels can be attached.
Generally, no hanging support wires are used where the ceiling is relatively of a short span between walls, as in a corridor. Hanging wire supports, extending from the structural ceiling to the beams, as well-known, are generally used where the spans are, for instance, 8 ft. or more.
In placing the ends of the beams on the wall molding ledge, much time and effort are expended in accurately positioning the beams along the ledge, and in securing the beam to the ledge. First, it is necessary to measure along the molding to locate the beam. Then, a self-tapping screw is manually inserted through the ledge and beam flange at one end of the beam. This requires the installer to hold the beam to the ledges until the screw, which is inserted from below, pierces through the flange. The screw then must be turned until the threads of the screw seat the head of the screw against the bottom of the ledge. Then, the operation is repeated at the other end of the beam. The procedure is repeated throughout the length of the ceiling.